The administration of proteins to animals, including humans, in nutritional supplements or as therapeutics has been known for some time. Proteins for therapeutic or nutritional administration generally are available either as (1) concentrates or powders that are administered directly or are reconstituted in a liquid of choice prior to use; or (2) liquid formulations.
The preparation and delivery of therapeutic proteins of interest in powder or particle form is an area of concentrated research and development activity in the pharmaceutical industry. For therapeutic efficacy, it is desirable to have a uniform formulation. For example, for pulmonary administration, the protein ideally is prepared in the form of discrete microspheres, which are solid or semi-solid particles having a diameter of between 0.5 and 5.0 microns. It also is desirable for the particles to have a protein content that is as high as possible and that maintains its activity for concentrated delivery and therapeutic efficacy.
Previous methods of producing protein microparticles or nanoparticles have involved complex steps, such as blending with organic polymers and/or forming a lattice array with polymers; spray drying, spray freeze-drying or supercritical fluid antisolvent techniques that use specialized and complex equipment; or lyophilization followed by pulverization or milling that often results in non-uniform particles that must further be sorted. Often previous methods of producing solid protein formulations involve processing steps, such as heating, that denature the protein and compromise its activity. In addition, some methods do not provide high recovery from solution into the solid formulation.
Accordingly, there is a need for a method for producing protein and other macromolecular microparticles that does not require complex or specialized equipment and that produces uniform-sized microparticles for delivery. There further is a need for a method of producing microparticles that contain high concentrations of the protein or macromolecule relative to other components, that are stable and maintain their activity for long periods of time when stored at ambient temperature and that do not contain a significant amount of denatured protein. There also is a need for a method of producing microparticles of proteins and other macromolecules wherein substantially all of the protein or macromolecule in the starting material is recovered in the microparticle formulation, with minimal loss. There also is a need for microparticles of proteins or other macromolecules containing these properties for administration, for example, as a therapeutic or nutritional supplement.